Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$153.31	13.562%	$174.1019	$174.10	$174.10	$174.10
Purchase #2	$78.89	10.180%	$86.921	$86.92	$86.90	$86.90
Purchase #3	$70.77	12.745%	$79.7896	$79.79	$79.80	$79.80
Purchase #4	$213.58	7.641%	$229.8996	$229.90	$229.90	$229.90
Purchase #5	$157.27	8.838%	$171.1695	$171.17	$171.15	$171.20
Purchase #6	$56.73	4.250%	$59.141	$59.14	$59.15	$59.10
Purchase #7	$236.94	10.389%	$261.5557	$261.56	$261.55	$261.60
7 purchase totals =	$967.49		$1,062.5783	$1,062.58	$1,062.55	$1,062.60